I know from their letters and tweets that my readers have been waiting patiently (mostly) for The Book of Dust for a long time. I've been writing it for several years, and I've been very parsimonious with information about it. It gives me great pleasure and some excitement at last to satisfy their curiosity (and mine) about this book.

What can I tell you about it? The first thing to say is that Lyra is at the centre of the story. Events involving her open the first chapter, and will close the last. I've always wanted to tell the story of how Lyra came to be living at Jordan College and, in thinking about it, I discovered a long story that began when she was a baby and will end when she's grown up. This volume and the next will cover two parts of Lyra's life: starting at the beginning of her story and returning to her 20 years later.

So, second: is it a prequel? Is it a sequel? It's neither. In fact, The Book of Dust is... an equel. It doesn't stand before or after His Dark Materials, but beside it. It's a different story, but there are settings that readers of His Dark Materials will recognise, and characters they've met before. Also, of course, there are some characters who are new to us, including an ordinary boy (a boy we have seen in an earlier part of Lyra's story, if we were paying attention) who, with Lyra, is caught up in a terrifying adventure that takes him into a new world.

Third: why return to Lyra's world? Dust. Questions about that mysterious and troubling substance were already causing strife 10 years before His Dark Materials, and at the centre of The Book of Dust is the struggle between a despotic and totalitarian organisation, which wants to stifle speculation and enquiry, and those who believe thought and speech should be free. The idea of Dust suffused His Dark Materials. Little by little through that story the idea of what Dust was became clearer and clearer, but I always wanted to return to it and discover more. Questions about our existence are infinitely interesting to me. There's always more to explore.

I've hugely enjoyed getting to know the new characters, seeing Lyra again, and exploring the world(s) they live in. I've loved watching the story expand across the years, and take me to places I'd never dreamed of. As for future volumes, my lips are sealed.